Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

INHA
81049
Inhibin A, Tumor Marker, Serum
Clinical Information: Inhibins are heterodimeric protein hormones secreted by granulosa cells of the
ovary in the female and Sertoli cells of the testis in the male. They selectively suppress the secretion of
pituitary follicle stimulating hormone (FSH) and also have local paracrine actions in the gonads. The
inhibins consist of a dimer of 2 homologous subunits, an alpha subunit and either a beta A or beta B
subunit, to form inhibin A and inhibin B, respectively. In females, inhibin A is primarily produced by the
dominant follicle and corpus luteum: whereas inhibin B is predominantly produced by small developing
follicles. Serum inhibin A and B levels fluctuate during the menstrual cycle. At menopause, with the
depletion of ovarian follicles, serum inhibin A and B decrease to very low or undetectable levels. Ovarian
cancer is classified into 3 types: epithelial, stromal sex cord, and germ cell tumors. Epithelial ovarian
tumors account for 90% of cases and are further subdivided into: serous (70%), mucinous (10%-15%),
and endometrioid (10%-15%) types. Granulosa cell tumors represent the majority of the stromal sex cord
tumors, which account for 2% to 5% of all ovarian tumors. Elevations of serum inhibin A and/or B are
detected in some patients with granulosa cell tumors. Inhibin A elevations have been reported in
approximately 70% of granulosa cell tumors. In these patients, inhibin A levels tend to show a 6-fold to
7-fold increase over the reference range value. The frequency of elevated levels varies amongst studies,
likely due to the different specificities of the antibodies used in the immunoassays. Inhibin A also appears
to be suitable markers for epithelial tumors of the mucinous type with about 20% of cases having elevated
inhibin A levels. In contrast, inhibin is not a very good marker in nonmucinous epithelial tumors. At best,
total inhibin is elevated in 15% to 35% of nonmucinous epithelial ovarian cancer cases. Inhibin seems to
be a complementary to cancer antigen 125 (CA 125) as an ovarian cancer marker. CA 125 is not as good
of a tumor marker for mucinous and granulosa ovarian cell tumors. Inhibin shows a better performance in
those 2 types of ovarian cancer. The majority of the studies for inhibin A and B as an ovarian cancer
marker have been limited to postmenopausal women where the levels for both proteins are normally very
low. Inhibin A has limited utility as an ovarian cancer marker in premenopausal women, where circulating
levels are higher and fluctuate throughout the menstrual cycle and, therefore, are difficult to interpret.
Useful For: An aid in the diagnosis of patients with granulosa cell tumors of the ovary when used in
combination with inhibin B Monitoring of patients with granulosa cell tumors and epithelial
mucinous-type tumors of the ovary known to secrete inhibin A
Interpretation: Inhibin A levels are elevated in approximately 70% of patients with granulosa cell
tumors and in approximately 20% of patients with epithelial ovarian tumors. A normal inhibin A level
does not rule-out a mucinous or granulosa ovarian cell tumor. Testing for inhibin B in these cases might
be informative as a higher proportion of mucinous or granulosa ovarian cell tumors will have an elevated
inhibin B level. Consider ordering INHAB/86336 ‘Inhibin A and B, Tumor Marker, Serum.†For
monitoring of patients with known ovarian cancer, inhibin A levels decrease shortly after surgery.
Elevations of inhibin A after treatment are suggestive of residual, recurrent, or progressive disease. In
patients with recurrent disease, inhibin A elevation seems to be present earlier than clinical symptoms.
Patients in remission show normal levels of inhibin A.
Reference Values:
Males: